Merging remote-sensing images for geological-environmental mapping: application to the Cabo de Gata-Níjar Natural Park, Spain

Abstract

 The Cabo de Gata Níjar Natural Park in Spain presents certain unique characteristics which make it of great geological, ecological and environmental interest. As a prior step to the environmental study of the park and the impact produced by the mining activities carried out up until ten years ago, the mining and waste-tip areas were defined and a lithological discrimination carried out. For this purpose, various remote-sensing techniques were employed to create high-resolution image documents on which the geological and environmental mapping of the area would be based, with special attention being paid to the areas of former mining activity because of its implications for the local environment. The merging of remote-sensing images with different spatial/spectral resolutions has become a highly useful tool, due to their increasing availability. Such is the case of the SPOT panchromatic and Landsat Thematic Mapper multispectral images, which are two of the most commonly used images in geological and environmental studies based on remote sensing. Of the numerous techniques described for merging remote sensing image data, this paper analyses those based on Intensity-Hue-Saturation, Principal Component Analysis, Spherical Coordinates, High-Pass Filters and Colour Normalized transform, using SPOT panchromatic and Landsat TM data. The research goals were (1) to analyse and compare some of the most commonly used methods; (2) to select the most appropriate method for a detailed geological-environmental study, and (3) to apply the methodology to the Cabo de Gata-Níjar area, the site of one of the most distinctive natural parks in the country.